Process Characteristics And Influencing Factors Of Forward Osmosis To Remove Antibiotics From Water

In recent years,the concentration of antibiotics in water has gradually increased,posing a threat to human health and the stability of the ecosystem.Forward osmosis can effectively remove antibiotics,but its operating conditions,the effect of coagulation pretreatment on the removal of antibiotics and membrane fouling under different conditions require further study.In this study,forward osmosis was used to remove antibiotics from water.Firstly,the changes of forward osmosis operation characteristics and rejection of antibiotic under different operating conditions were studied.Then the effect of coagulation on the removal of antibiotics by forward osmosis and the mechanism of membrane fouling were studied.Finally,the membrane fouling and membrane cleaning efficiency during the process of antibiotics removal by forward osmosis were analyzed.The paper first studied the effects of membrane orientation,draw solution concentration,water temperature and flow velocity on water flux,NaCl reverse flux and antibiotics rejection.The rejection of the single antibiotics ceftazidime(CAZ),cefepime(FEP)and two antibiotic coupling rejection were compared.The results showed that the rejection of two antibiotics coupling was 2%-5%higher than that when they existed separately.This is due to the enhanced steric hindrance between organic molecules.In addition,the antibiotic rejection increases with the increase of salt reverse flux.On this basis,the influence of coagulation on forward osmosis was explored.The pretreatment effect of three coagulants-PAC?FeC13 and Al2(SO4)3 on humic acid(HA)simulated wastewater which containing CAZ was' investigated.The pretreated water samples were subjected to forward osmosis experiments.The changes of water flux,NaCl reverse flux and antibiotic rejection were analyzed.The HA removal rate,antibiotic rejection,chroma and Zeta potential in feed solution were changed by coagulation pretreatment.After pretreatment,the water flux reached the maximum under the optimal dosage of three coagulants,which were 7.2-10.9 L/(m2·h)?9.1-11.9 L/(m2·h)?8.1-11.0 L/(m2·h)respectively.The NaCl reverse flux decreased with the increase of the contaminated layer thickness,while the CAZ rejection increased,reaching a maximum of 97.1%.After experiment,the fouling membrane was cleaned,and the cleaning speed and cleaning time had a great influence on the membrane flux recovery rate.The membrane flux recovery rate was above 70%after cleaning.The study also investigated membrane fouling and membrane cleaning efficiency under different conditions.The contaminated layer was formed on the surface of the active surface in FO mode,resulting in a decrease in water flux.The increase of draw solution concentration and reverse diffusion of Mg2+ in draw solution promoted the formation of the contaminated layer.Contaminants entered the interior of the support layer in PRO mode,increasing the degree of membrane fouling,and then resulting in a rapid decrease in water flux.The fouling layer formed in FO mode is denser than that in PRO mode,and the steric hindrance effect on antibiotic is stronger,and the CAZ rejection is about 8%higher than the PRO mode.In addition,the membrane flux recovery rate is higher in FO mode.For thicker contaminated layers,the cleaning time should be extended,and towards denser contaminated layers,the cleaning speed should be increased.After cross flow cleaning,the membrane flux recovery rate was less than 50.2% in the PRO mode.